[Show abstract][Hide abstract] ABSTRACT: This article describes the results of simulations of CO oxidation under low pressure conditions over a bimetallic Pt/Rh composite catalyst. The model is represented by a system of four differential–algebraic equations (DAEs) for the coverages of COads and Oads, on the two parts of the composite surface. Surface diffusion of both adsorbates is assumed to be fast. The experimentally observed synergetic effect concerning CO oxidation on a Rh surface partly covered by Pt monolayer islands is reproduced in the simulations. It is shown that this synergetic effect is due to the difference in the CO sticking coefficients on Pt and Rh surfaces. In addition, a new type of kinetic oscillations, namely “synergetic kinetic oscillations” are predicted by the simulations. These oscillations exist under conditions at which no oscillations can exist over Pt and Rh monometallic catalysts. The driving force of this new type of oscillations is connected to the large difference in binding energy of adsorbed oxygen atoms on Rh and Pt.
Chemical Engineering Journal 02/2015; DOI:10.1016/j.cej.2015.02.050 · 4.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A hydrodehalogenation (HDC) reaction of trichloroethene (TCE) has gained a lot of interest due to its possible application in water purification, but the reaction mechanism has been subject to much controversy. In this work, HDC of TCE on Pd(111) was examined by carrying out kinetic Monte Carlo simulations based on DFT-calculated thermodynamic and kinetic parameters. Obtained kMC results show that the HDC follows a so-called direct pathway, which means that, after adsorption on a catalyst, TCE quickly dechlorinates, producing CH-C and then, more slowly, hydrogenates to form hydrocarbon products. This is reflected in the surface coverage snapshots, where intermediates corresponding to the direct pathway are mostly seen. We also investigated the effect of lateral Cl-Cl repulsions on the distribution and coverage of intermediates, and on the reaction mechanism. In general, the adsorbed Cl atoms retard further dechlorinations, leading to less effective HDC, which is in line with experimental observations.
The Journal of Physical Chemistry C 08/2014; 118(34):19759-19767. DOI:10.1021/jp503494g · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The deposition of the chalcopyrite light absorbers onto the back contact of thin films solar cells involves the adsorption of Se on Mo surfaces, to form an intermediate MoSe2 layer. Together with Se and the other elements composing the absorber, also impurities like oxygen and sodium are present in common processing technologies. In order to promote the understanding of atomic mechanisms and basic thermodynamic parameters related to deposition, we predict the adsorption energies and most stable adsorption sites of Se, O and Na on the Mo(110) surface using first principles calculations, based on density functional theory. We discuss implications for kinetics on the surface.
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